This invention relates generally to a system for loading and masking substrates in association with a sputter deposition system.
A conventional optical disk includes a plastic base upon which layers of various materials, such as metals, alloys, or dielectrics, are applied. One method of applying the layers of materials is to use a sputter deposition process.
A conventional sputter deposition process is performed using a plasma formed in a vacuum chamber of a sputter deposition system. The plasma is generated by applying electric. power to a low pressure gas in the vacuum chamber. Ions originating within the plasma bombard a target formed of a material that is to be deposited on the optical disk. The bombarding ions eject material from the target. The ejected material deposits in a layer on the disk.
A conventional sputtering system known as the BALZERS(trademark) BIG SPRINTER(trademark) is believed to include a loadlock between a main vacuum chamber and a disk loader robot. The disk loader robot includes two opposing arms, each of which includes an identical disk holder. An external robot loads an unprocessed optical disk (or other substrate) into the disk holder, and unloads a processed disk from the disk holder. The disk loader robot rotates 180xc2x0, and thereby alternatively positions each disk holder at the loadlock and the external robot.
During the sputtering operation, the two masks, one known as an inner mask and one as an outer mask, prevent deposition on the central and peripheral portions of the disk, respectively. The inner mask consists of a solid cylindrical body with an annular head attached to one end of the cylindrical body. At the outside of the cylindrical body is a spring mechanism that traps the disk under the annular head. The outer mask is in shape of a flat ring. The disk holders and the carrier arm hold the masks using magnets. The annular head of the inner mask and the surface of the outer mask that faces in the same direction as the sputtered surface of the disk both get a coating of the sputtered material. Magnetized components of the disk holder and the carrier arm contact the sputtered surfaces of the inner and outer masks during loading and handling processes.
The sputter-coated inner and outer masks need to be replaced periodically. To do this, the disk loader robot is rotated 90xc2x0, thereby placing the disk holder with the masks that are to be replaced at a station dedicated to changing of the masks.
There are drawbacks to the above described system that heretofore have not been resolved. First, contacting the sputtered surfaces of the inner and outer masks dislodges sputtered material from the masks, causing particulate contamination on the disk and in the sputtering system. Second, the masks get hot in the vacuum chamber, and have limited opportunities to cool. The hot masks can cause heat damage to the surface of the disk. Third, the use of magnets near the substrate to hold the masks affects the plasma, thereby affecting the uniformity of the film. Fourth, the sputtering system includes a station dedicated to changing of the masks, which consumes valuable space in the machine.
The present invention overcomes the aforesaid shortcomings of the prior art, while at the same time providing a high throughput and reliable system for loading, unloading, handling, and masking substrates, such as optical disks, that are. to be coated with a sputtered material. The surfaces of the masks that are subjected to direct sputter deposition (i.e., the surfaces that face in the same direction as the coated surface of the substrate) are not handled, which avoids the particulate contamination seen in the prior art system.
A sputtering system within the present invention includes a substrate handling system. The substrate handling assembly moves individual unprocessed disks (i.e., disks to be sputter coated) between a disk change station, which is external to the sputtering system, and a loadlock of the sputtering system. The substrate handling assembly moves individual processed disks (i.e., coated disks) between the loadlock and the disk change station. An inner mask and an outer mask accompany each unprocessed disk from the external disk change station, through the sputtering system, and back to the disk change station.
The substrate handling system includes one or more arms. At the end of each arm is a disk and mask handling assembly, which is called an xe2x80x9cend effectorxe2x80x9d herein. In one embodiment, the end effector comprises a lid that fits over an access opening to the loadlock. The end effector also includes an inner mask gripper and an outer mask gripper. The inner mask gripper grips the inner mask, and the outer mask gripper grips the outer mask.
The inner mask is generally mushroom shaped and fits in a hole in the center portion of the disk. Unlike the prior art inner mask, however, the inner mask of the present invention has a central cylindrical opening that is accessed through the annular head. The inner mask gripper grips the inner mask on a sidewall surface within the cylindrical opening that is not subjected to direct sputter deposition.
The outer mask has a hollow vertically-extending body with a central opening that is sized so that a disk can be horizontally disposed within the central opening. A lip at the top of the body superimposes a circumferential portion of the disk. The outer mask gripper grips the outer mask on an outer surface of a vertically-extending sidewall of the body of the outer mask. The gripped surface is not subjected to direct sputter deposition.
In one embodiment, the substrate handling system operates by positioning an end effector that is gripping an inner mask and an outer mask at the external disk change station. An unprocessed disk is placed and centered on the inner mask and within outer mask. The substrate handling system moves the end effector to the loadlock, places the unprocessed disk and masks into the loadlock, and seals the access opening to the loadlock with the lid. The end effector pushes the inner mask and outer mask onto a substrate transfer tray positioned in the loadlock. The masks are released by the end effector. The disk and its accompanying inner and outer masks then move on the tray to a sputtering station. Subsequently, after a tray having a processed disk and inner and outer masks is moved into the loadlock, the load lock is vented, and the end effector at the loadlock grips the inner and outer masks on unsputtered surfaces thereof, thereby capturing the processed disk. The substrate handling system moves the end effector to the disk change station, where the processed disk is removed from the inner and outer masks. The cycle subsequently repeats. The design of the system allows high throughput loading and unloading of the disks.
Further features and advantages of the invention will become apparent in view of the drawings and detailed description of the exemplary embodiments.